Recent advances in informatization have led to an increase in demand for data communication traffic in data communication and the like. Accordingly, there are network-related needs for broader bandwidths and lower operation costs. Mobile telephone networks and the like utilize networks constructed by radio links including Fixed Broadband Wireless Access (FWA) which is based on a radio system utilizing a frequency such as a millimeter waveband that enables broadband transmission.
The communication quality of each radio link varies depending on a signal-to-noise ratio (SNR) of a received signal. In this regard, an adaptive modulation technique is employed to achieve a broader bandwidth of each radio link. The adaptive modulation technique is a technique that adaptively finds and uses a modulation mode with a highest transmission efficiency depending on the radio condition of each radio link. The use of the adaptive modulation technique enables optimum radio communication depending on the radio environment, which leads to an improvement in frequency efficiency.
If the modulation mode to be used in the future by each radio link can be predicted, the communication quality of traffic flowing through a network can be guaranteed. An example of a radio link using the adaptive modulation technology is disclosed in Published Japanese Translation of PCT International Publication for Patent Application, No. 2006-505221. As described in this literature, since a radio link using the adaptive modulation technology may have a certain degree of correlation with a past history, the modulation mode to be used by the radio link can be predicted (estimated).
Additionally, Non Patent Literature 1 discloses a path control method that ensures a communication quality, which is required by a flow, by using an index “stability” indicating how stably the bandwidth of each radio link can be used, due to the fact that the bandwidth of each radio link is changed by adaptive modulation.